1. Field of the Invention
The present invention generally relates to a safe, portable chemical combination of reagents which, when combined, conveniently and safely generates heat, steam and a biocidal chemical agent that destroys contaminating microorganisms or chemical agents on contaminated objects or surfaces. The present invention does not require external sources of power such as electricity or fire.
2. Description of Related Art
Microbial contamination of objects and surfaces such as food contact surfaces and food service equipment in kitchen environments (e.g., cutting boards, knives, and utensils), of military clothing, vehicles, and equipment, and of medical, dental, or veterinary instruments can lead to the transmission of infectious pathogens and the spread of food-borne illnesses and other diseases. Inactivating these pathogenic microorganisms to prevent infection and the spread of disease requires disinfection or sterilization through the application of a lethal treatment of commensurate stringency.
Military activities in remote or open field locations often experience conditions wherein electrical power, water, or fire is unavailable, of limited availability, or undesirable in such environments. Military surgical teams in such instances require clean, safe, sterile instruments and equipment that contact the patient. While pre-packaged instruments transported to these locations arrive initially sterile, they become contaminated following their use in medical procedures. It is absolutely necessary that these contaminated instruments be cleaned and sterilized before subsequent use on other patients to prevent the transmission of infection and disease.
In representative hospitals, clinics, and laboratories, contaminated instruments are customarily washed, scrubbed, sealed in germ-free packaging, and then sterilized in an autoclave for re-use. Typically, pressurized steam autoclaves powered by electrical power generate heat and/or steam as the agents most frequently used to sterilize glass, metal, or high-melting plastic tools and instruments. However, it is currently not possible to carry out such sterilization techniques in military facilities located in remote or open field environments where large pressurized steam autoclaves are not available, and wherein electrical power, water, or fire is unavailable, of limited availability, or undesirable. The challenge of replenishing the supply of available sterile instruments in these circumstances often requires transporting contaminated equipment via aircraft to distant hospitals with the facilities to support the operation of a pressurized steam autoclave. In order to safely and effectively sterilize contaminated surgical instruments for immediate re-use on site in these remote or difficult-to-access locations with limited power supplies, it is necessary to consider alternatives to electrical or fossil fuel-powered sterilization using autoclaves.
There are several prior art sterilization methods used to sterilize objects such as field feeding equipment, military equipment, or surgical tools. However, such prior art methods are not suited for remote, field environments such as those typically found in military situations or in countries ravaged by disease and famine wherein international health workers and doctors conduct medical operations in situ. The most widely used chemical disinfectants are halogens, ozone, chlorine dioxide, chloramines, and ethylene oxide. Among them, the most effective disinfectant is chlorine. Ozone and chlorine dioxide are very close to chlorine with respect to effectiveness. Other halogens, such as bromine and iodine, are less effective as is ethylene oxide, although, under certain circumstances, one of these agents may be recommended over the others. For example, ethylene oxide is frequently used to fumigate textiles because ethylene oxide is readily decomposed to non-toxic products on contact with air.
The major disadvantages of the two most effective chemical disinfectants, i.e. chlorine and ozone, are problems related to their storage, transport, and generation. Chlorine is stored as a gas in heavy pressurized cylinders. Ozone is unstable, and is generated in situ, which requires a source of electricity. Heavy equipment is typically involved whether electrical power is obtained from batteries or generators. Ozone, moreover, is usually generated in an electrochemical cell which must be continuously supplied with air at one electrode and water at the other electrode thereby necessitating the use of further mechanical and/or electrical implements and devices. Other halogens and traditional disinfectants, such as hydrogen peroxide, chloramines, and ethylene oxide, are unstable, not sufficiently effective, or are difficult to handle.
Another technique for sterilizing or disinfecting objects entails the use of the disinfectant Super Tropical Bleach (sodium hypochlorite in aqueous solution). This bleach is typically used to decontaminate military equipment, vehicles, weapons, clothing, and field-kitchen equipment. However, hypochlorite cannot be generated on-site and must be transported and stored in large, heavy containers. Hypochlorite is also caustic and difficult to ship due to its potential health hazards. Furthermore, hypochlorite is especially corrosive to metal surfaces such as those found on military equipment, vehicles, weapons systems, and generators. Additionally, disinfection or decontamination by hypochlorite produces environmentally hazardous by-products including carcinogenic compounds that endanger human health. These disadvantages of Super Tropical Bleach prevent its use in disinfecting contaminated surgical instruments in remote or far-forward environments.
The use of radiation to achieve disinfection and sterilization also has many disadvantages. Whether the radiation takes the form of ultraviolet light, X-rays, or nuclear emissions, it is usually applied in an enclosed environment. The generation of such high-energy radiation either involves electricity, for ultraviolet light and X-rays, or lead-lined containers and special handling, in the case of shielded installations for radioactive nuclides. Factors such as high power, heavy and complex equipment and extreme safety precautions preclude the rapid deployment of radiation sources from one location to another, especially in remote areas.
Thus, these aforesaid sterilization and disinfection methods that use chemicals or radiation are not suitable for remote, field operations and in situations wherein electrical power is not available or of limited availability.
Another known sterilization and disinfection technique involves chlorine dioxide synthesis. Known chlorine dioxide synthesis techniques typically use one of three methods: (a) electrochemical, (b) acidification, and (c) oxidation. Each of these three methods is described in the ensuing description.
(a) Electrochemical Methods
The electrochemical methods involve the formation of chlorine dioxide from chlorine-containing compounds of lower chlorine oxidation number, such as, but not limited to, chloride, hypochlorite, or chlorite ions, by passage of an electrical current through solutions of these electrolytes in an electrochemical cell. For example, Tremblay et al. Patent Application Publication No. U.S. 2003/0006144 discloses an electrochemical method that requires the production of relatively large volumes of electrolyte that must be constantly stirred and transported in small amounts using an electrochemical cell. The electrochemical cell typically comprises liquid reservoirs, pumps, and batteries which are not only heavy, voluminous and bulky, but also are difficult to operate without a source of electricity or fire. Furthermore, although potable drinking water can be produced from such an electrochemical cell, Herrington U.S. Pat. No. 6,736,966 does not disclose achievement of sterilization, the more rigorous state of complete elimination of microorganisms.
(b) Acidification
Acidification involves the formation of chlorine dioxide by proton transfer to chlorite ion. The chlorous acid so produced disproportionates to yield chloride and chlorate ions, and various amounts of chlorine dioxide. Kampa Patent Application Publication No. U.S. 2004/0062680 (“Kampa”) discloses an apparatus and method wherein the components needed for reaction are sequestered into two compartments separated by a rupturable membrane. This method can be used for acidification if a component in one compartment is a proton-releasing reagent, and the other component in the second compartment is a chlorite salt. Such a technique is prone to several problems the solutions of which make the techniques disclosed in Kampa undesirable for field sterilization. For example, the acidification reactions may be too slow and require expensive catalysts that do not last long as is found in Ostgard U.S. Pat. No. 6,399,039. Barenberg et al. U.S. Pat. No. 5,980,826 (“Barenberg”) discloses a chemical combination which is a variation on the acidification method and uses a hydrophobic material to contact a contaminated surface, a hydrophilic material to introduce water needed to release protons, a proton-releasing reagent and a chlorite salt. However, the chemical combination described in Barenberg requires bulky material and precise control in order to achieve the correct amount of moisture in the atmosphere. Thus, the technique described in the aforesaid Barenberg patent is not suited to the rigorous sterilization requirements associated with remote field operations as is frequently found in military applications (e.g., high altitudes or desert climates). Klatte U.S. Pat. No. 6,635,230 describes a technique involving the use of a zeolite to store the proton-releasing compound and chlorite salt in a mixed, but unreactive state. However, such a technique uses costly materials, requires fluid flow methodologies, and is not suited to the sterilization requirements associated with remote sites wherein electrical power is not available.
(c) Oxidation
Oxidation methods require the formation of chlorine dioxide by using a chemical oxidant to raise the oxidation number of a chlorine-containing chemical such as sodium chlorite. A widely used oxidant is chlorine gas, which must be transported to the site in a heavy pressurized gas cylinder. In addition, there are problems in gas delivery which require considerable heavy, energy-consuming equipment to make the device effective as a biocide. Such a technique is disclosed in Jefferis, III et al. U.S. Pat. No. 4,908,188.
Thus, as shown above, none of these aforementioned chlorine dioxide synthesis methods provide a safe, convenient, reliable means for generating sufficient chlorine dioxide to achieve sterilization of objects in a relatively short time and in remote locations.
There are also disinfection methods and techniques that do not use chlorine dioxide. Such a method is described in Tarancon U.S. Pat. No. 5,229,072. This technique uses a fluorine-containing interhalogen compound such as gaseous chlorine trifluoride which hydrolyzes upon contact with liquid water or gaseous water vapor to release biocidal products. This technique necessitates the safe handling of corrosive and expensive materials as well as toxic gases. Furthermore, this technique requires a chamber of controlled humidity to effectuate disinfection. Thus, this technique is not suited for remote field operations.
There are other prior art techniques and methods that are variations of the techniques and methods described in the foregoing description. For example, Rosenblatt et al. U.S. Pat. No. 4,504,442 also discloses the use of chlorine dioxide gas as a chemosterilizing agent. Contaminated surfaces are contacted with an effective amount of gaseous chlorine dioxide for a predetermined amount of time to kill bacterial spores at a temperature that does not overly exceed ambient temperature. Rosenblatt et al U.S. Pat. No. 4,681,739 discloses the use of chlorine dioxide gas as a chemosterilizing agent. The method comprises the step of exposing a surface contaminated with spores to a humid gaseous environment and then exposing the spores to an amount of gaseous chlorine dioxide. Drake U.S. Pat. No. 6,042,802 discloses a method and apparatus for generating and using chlorine dioxide. Specifically, this patent teaches a method for generating a volume of disinfectant/sterilant fluid having a predetermined concentration of chlorine dioxide. The method includes transferring the generated chlorine dioxide gas to a separate disinfectant chamber containing a liquid solvent. The liquid solvent is chosen from the group consisting of water, alcohol, organic solvents and chlorinated solvents.
Aoyagi U.S. Patent Application No. U.S. 2003/0136426 discloses a method for cleaning and sterilizing medical devices. The medical devices are immersed in a chlorine dioxide solution. Thereafter, the medical device is placed in a chlorine dioxide gas atmosphere. Nelson et al. Patent Application Publication No. U.S. 2004/0101438 discloses a method and apparatus for sterilizing or sanitizing a container for food. Chlorine gas is produced either inside or outside the container and then circulated inside and throughout the container. The chlorine gas is then removed from the container and is reclaimed by dissolving it in a solvent. However, the foregoing techniques and methods suffer from one or more of the drawbacks and disadvantages described in the foregoing description (i.e. complex, bulky and expensive equipment, equipment that requires electrical power, etc.) and therefore, are not suited for use in remote locations wherein electrical power is not available or of limited availability, or wherein fire is either not available or undesirable.
Thus, it is apparent that currently, there is no portable, power-free method to safely, conveniently, and controllably generate sterilant or disinfectant in field environments, particularly in remote locations, that can be used to sanitize field feeding equipment, decontaminate military clothing or equipment, or sterilize medical instruments. With respect to sterilizing contaminated medical or surgical instruments, there is currently no alternative to the costly and inconvenient practice of collecting the used medical or surgical instruments and tools, removing them from the remote field environment, and transporting them to a distant site where they are sterilized in electrically-powered hospital steam autoclaves, packaged, and then transported back to the remote field environment for reuse. What is needed is a technique whose precursors can be safely and readily transported to field locations (including difficult-to-access environments or remote locations) and that requires no external power sources to controllably and safely generate a lethal biocidal chemical agent to sterilize objects or surfaces (e.g. field feeding equipment, medical instruments, military clothing or equipment, etc.) on site so that such objects can be cleaned, sterilized, and reused quickly and safely.